Abstract

Chromosomes, as the carriers of the genes which transmit hereditary characteristics, have always excited attention among biologists. In the late nineteenth century it became clear that each species had a constant number of chromosomes, and that this number was invariable within the species. Attempts were made to determine the chromosome number in man by Hansemann as early as 1891,1 but no convincing answer to this problem came until 1912, when de Winiwarter reported 47 chromosomes in spermatogonial metaphases.2 This continued to be controversial until about 1921, when Painter3 appeared to settle all doubts by demonstrating an additional small chromosome, the